1. Field of the Invention
This invention relates to a motor control device, and more particularly to a motor control device suitable for driving the picture-taking lens moving motor of the automatic focusing apparatus of a camera.
2. Description of the Prior Art
As a focus detecting device for detecting the condition of focusing of the picture-taking lens of a camera with respect to an object to be photographed, a device which produces three different signals to control the driving device of a motor for driving the focusing optical system of the picture-taking lens, namely, a front focus signal for moving the optical system in one direction during the front focus condition in which the picture-taking lens is focused to the front side of a major object to be photographed, a rear focus signal for moving the optical system in the other direction during the rear focus condition in which the picture-taking lens is focused to the rear side of the major object, and an in-focus signal for stopping the movement of the optical system when the picture-taking lens has become in-focus to the major object has already been proposed in U.S. application Ser. No. 167,912 filed on July 11, 1980 by the applicant and corresponding German Laid-open Patent (DOS) No. 30 27 729. The above-described driving device for causing the rotation of the motor to respond to such three different signals is usually provided with three input terminals to operate switching elements for forming the forward rotation circuit, the reverse rotation circuit and the circuit for suddenly stopping the motor, respectively. Particularly, in a camera wherein the camera body and the picture-taking lens sturcture are separable from each other, when it is taken into account that a signal is transmitted from the focus detecting device provided in the camera body to the driving device provided in the lens structure, at least three electrical contacts are required between the camera body and the lens structure to transmit respective signals to three input terminals. An increase in the number of such electrical contacts is inconvenient for the designing of modern cameras in which transmission of numerous types of information must be made possible between the camera body and the lens.